The objective of this project is the characterization of a recently defined veterinary pathogen--Contagious Equine Metritis Organism (CEMO). Clinically contagious equine metritis (CEM) shares some of the features of gonorrhea in humans. Specifically leukorrhea, silent infections, chronic infections, and the generation of nonprotective antibodies during the course of infection occur in both diseases. Interest in CEM as a possible animal model for gonorrhea and interest in the mechanisms of pathogenesis prompted these studies. The project is multifaceted; specific aspects include (1) ultrastructural analysis of colonial variants of three strains, (2) analysis and comparison of the major outer membrane protein (MOMP), (3) analysis of strain specific surface proteins, (4) isolation and characterization of capsule and lipopolysaccharide, and (5) production of monoclonal antibodies to surface proteins, capsule and LPS. Like Neisseria gonorrhoeae, organisms grown on clear typing medium express colonial phenotypic variation. Opaque and transparent phenotypes have been isolated, cloned and evaluated. Unlike the gonococcus, the basis for opacity variation does not appear to correlate with protein variation. In addition, several capsule/LPS mutants have been isolated based on a colonial characteristic of intermediate opacity. The organism produces large amounts of extracellular material, capsule. This capsule, likely carbohydrate in composition, is extremely antigenic in experimentally infected horses and hyperimmunized rabbits. The MOMP of CEMO has been evaluated by SDS-PAGE, it has the same Mr as MOMP of N. meningitidis (41K). Two-dimensional peptide maps of MOMPs from these two species are remarkably similar. Other surface constituents of interest include several strain specific proteins (these are antigenic) and the LPS. We are producing monoclonal antibodies to CEMO surface constituents and presently have two--one reactive with capsule and one with MOMP.